From: Mike Snitzer <snitzer@redhat.com>

If CONFIG_DM_DEBUG_SPACE_MAPS is enabled and memory is fragmented and a
sufficiently-large metadata device is used in a thin pool then the space
map checker will fail to allocate the memory it requires.

Switch from kmalloc to vmalloc to allow larger virtually contiguous
allocations for the space map checker's internal count arrays.

Reported-by: Vivek Goyal <vgoyal@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

---
drivers/md/persistent-data/dm-space-map-checker.c |   28 ++++++++++++--------
 drivers/md/persistent-data/dm-space-map-checker.c |   30 +++++++++++++---------
 1 file changed, 19 insertions(+), 11 deletions(-)

Index: linux-3.5-rc5/drivers/md/persistent-data/dm-space-map-checker.c
===================================================================
--- linux-3.5-rc5.orig/drivers/md/persistent-data/dm-space-map-checker.c
+++ linux-3.5-rc5/drivers/md/persistent-data/dm-space-map-checker.c
@@ -8,6 +8,7 @@
 
 #include <linux/device-mapper.h>
 #include <linux/export.h>
+#include <linux/vmalloc.h>
 
 #ifdef CONFIG_DM_DEBUG_SPACE_MAPS
 
@@ -89,13 +90,23 @@ static int ca_create(struct count_array 
 
 	ca->nr = nr_blocks;
 	ca->nr_free = nr_blocks;
-	ca->counts = kzalloc(sizeof(*ca->counts) * nr_blocks, GFP_KERNEL);
-	if (!ca->counts)
-		return -ENOMEM;
+
+	if (!nr_blocks)
+		ca->counts = NULL;
+	else {
+		ca->counts = vzalloc(sizeof(*ca->counts) * nr_blocks);
+		if (!ca->counts)
+			return -ENOMEM;
+	}
 
 	return 0;
 }
 
+static void ca_destroy(struct count_array *ca)
+{
+	vfree(ca->counts);
+}
+
 static int ca_load(struct count_array *ca, struct dm_space_map *sm)
 {
 	int r;
@@ -126,12 +137,14 @@ static int ca_load(struct count_array *c
 static int ca_extend(struct count_array *ca, dm_block_t extra_blocks)
 {
 	dm_block_t nr_blocks = ca->nr + extra_blocks;
-	uint32_t *counts = kzalloc(sizeof(*counts) * nr_blocks, GFP_KERNEL);
+	uint32_t *counts = vzalloc(sizeof(*counts) * nr_blocks);
 	if (!counts)
 		return -ENOMEM;
 
-	memcpy(counts, ca->counts, sizeof(*counts) * ca->nr);
-	kfree(ca->counts);
+	if (ca->counts) {
+		memcpy(counts, ca->counts, sizeof(*counts) * ca->nr);
+		ca_destroy(ca);
+	}
 	ca->nr = nr_blocks;
 	ca->nr_free += extra_blocks;
 	ca->counts = counts;
@@ -151,11 +164,6 @@ static int ca_commit(struct count_array 
 	return 0;
 }
 
-static void ca_destroy(struct count_array *ca)
-{
-	kfree(ca->counts);
-}
-
 /*----------------------------------------------------------------*/
 
 struct sm_checker {